The present invention relates to the fabrication of integrated circuits. More specifically, embodiments of the invention pertain to methods of removing residue from the interior surfaces of a substrate processing chamber.
One of the primary steps in the fabrication of modern semiconductor devices is the formation of a layer, such as a silicon oxide layer, on a substrate or wafer. As is well known, such a layer can be deposited by chemical vapor deposition (CVD). In a conventional thermal CVD process, reactive gases are supplied to the substrate surface where heat-induced chemical reactions take place to form the desired film. In a conventional plasma CVD process, a controlled plasma is formed using radio frequency (RF) energy or microwave energy to decompose and/or energize reactive species in reactant gases to produce the desired film.
Unwanted deposition on areas such as the walls of the processing chamber also occurs during such CVD processes. As is known in the industry, it is common to remove the unwanted deposition material that builds up on the interior of chamber walls with an in situ chamber clean operation. Common chamber cleaning techniques include the use of an etchant gas, such as fluorine, to remove the deposited material from the chamber walls and other areas. In some processes, the etchant gas is introduced into the chamber and a plasma is formed within the chamber so that the etchant gas reacts with and removes the deposited material from the chamber walls. Such cleaning procedures are commonly performed between deposition steps for every wafer or every n wafers.
Some semiconductor manufactures employ a remote plasma cleaning process as an alternative to an in situ plasma cleaning, a remote plasma cleaning procedure may be employed in which a plasma is generated remote from the substrate processing chamber by a high density plasma source such as a microwave plasma system, toroidal plasma generator or similar device. Dissociated species from the plasma are then transported to the substrate processing chamber where they can react with and etch away the undesired deposition build-up. Remote microwave plasma cleaning procedures are sometimes used by manufacturers because they provide a “softer” etch than in situ plasma clean operations, i.e., there is less ion bombardment and/or physical damage to chamber components because the plasma is not in contact with chamber components.
Regardless of whether an in situ or remote cleaning process is employed, over time, residue may build up within the chamber that cannot be removed by standard dry cleaning processes. Accordingly, many semiconductor manufacturers use a wet cleaning process to remove such residue. One commonly used wet clean process includes removing appropriate components of the chamber (e.g., chamber liners, the gas manifold or gas nozzles, and the pedestal) and dipping the components in a bath of hydrofluoric acid (HF). Components that cannot easily be dipped in such a bath, e.g., the interior chamber walls, are instead wiped with an HF or similar solution.
As can be appreciated, wet cleaning operations require the substrate processing tool to be taken offline. This results in a decrease in wafer throughput and a general desire on behalf of the semiconductor manufacturers to use such wet cleaning processes less frequently than dry cleaning processes. As an example of frequency of use, during the use of one known semiconductor substrate processing tool used to deposit a silicon oxide dielectric layer over a substrate, the chamber is dry cleaned using a remote plasma clean process after every 5th substrate processed in the chamber, while the chamber is cleaned using a wet clean process every 5000 wafers.
While wet clean processes such as the HF clean just described have been used successfully by a number of different semiconductor manufacturers, improved cleaning processes are desirable.